Apparatus for automatic sensing of line amplifier configuration for status monitoring

ABSTRACT

An apparatus for indicating the configuration of a cable television line amplifier. The line amplifier contains a controller that senses a preset voltage on a status indication line. When the amplifier is reconfigured, such as by adding new circuits containing new functions or features, these new circuits contain resisters that are shunted to modify the preset voltage level on the appropriate status indication line. The controller senses the modified voltages and provides an indication of the new function of the new circuit to a headend through a cable television distribution system.

This application claims the benefit of 60/019,007 filed Jun. 3, 1996.

BACKGROUND OF THE INVENTION

This invention relates to an apparatus for sensing the configuration ofa cable television line amplifier and more particularly to an apparatusthat detects different modules plugged into a line amplifier, andtransmits the configuration of the modules to a headend controller.

Line amplifiers are commonly used in cable television distributionsystems to extend the range that television signals are transmitted.Line amplifiers contain different modules that have a variety offunctions. The functions include automatic gain control (AGC) control,monitoring, reverse path amplification and multiple amplified outputports. With present cable TV distribution systems, the system operatormust rely on installation notes from a technician when configuring hisline amplifiers. The technician uses the notes to configure the lineamplifier by setting jumpers on a module in the line amplifier or byentering data in the memory of the module. Inaccurate notes could resultin lost time to set up the line amplifier station. Incorrect entry ofthe data into the module could result in faulty operation of theamplifier.

SUMMARY OF THE INVENTION

The invention permits a status monitoring module within a line amplifierto be automatically configured upon installation without the technicianhaving to enter data or set jumpers within the module, regardless of thenumber of module types that are installed. The invention will also allowamplifier configuration changes in the field to be completedelectronically and instantaneously without the technician having tochange the module switch settings or without requiring the re-enteringof data in the module. The status monitor utilizes A/D inputs to read DCvoltages supplied by the various modules. These voltages represent theamplifier's configuration. In response to different modules being addedto the line amplifier, these voltages would automatically change uponthe addition of a module with a new option. A controller within the lineamplifier would then read the voltage change and send a signal eitherover the distribution system to a headend or locally to a test point onthe line amplifier indicating a change in the amplifier's configuration.

The foregoing and other objects of the present invention a well as theinvention itself, may be more fully understood from the followingdescription when read in conjunction with the accompanying drawings.

DESCRIPTION OF THE FIGURES

FIG. 1 is a simplified block diagram of a line amplifier implementingthe invention; and

FIG. 2 is a simplified block diagram of the status monitoring deviceshown in FIG. 1 and incorporating the features of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a dual line amplifier 10 having aninput port 14 coupled through cable 11 to a headend controller 12.Amplifier 10 has output ports 21 and 22 coupled to subscribers 16.Amplifier 10 includes amplification circuitry 20, monitoring circuitry24 and a removable module containing reverse path circuitry 26.Amplification circuitry 20 amplifies the signal on port 14 beforefeeding it to output ports 21 and 22. Circuitry 24 contains an RF detectcircuit 50, status monitor circuitry 30, indicator circuitry 64 and amodularized and removable AGC control circuit 52. Monitoring circuitry24 determines the configuration of line amplifier circuitry 20, storesthis configuration and feeds a signal indicative of the configurationthrough reverse path circuitry 26 to headend controller 12. Monitoringcircuitry 24 internally generates one or more preset signals having avoltage level references. These signals are fed to status monitorcircuit 30. The voltage level references of these signals change whenthe amplifier 10 is reconfigured, thereby providing an indication tostatus monitor circuit 30 of the current state of the amplifierconfiguration.

Amplifier 10 receives an RF signal on input port 14 that is fed throughhigh/low filter 18, equalizer 32, and amplified by amplification stage34. The output of the amplification stage 34 is fed through variableloss inserter 36, or attenuator, and directed through coupler 38 tooutput amplifiers 42 and 44. The output of amplifiers 42 and 44 are fedthrough filters 46 and 48, respectively, to output terminals 21 and 22.The outputs of amplifiers 42 and 44 are also fed to monitoring circuitry24.

Monitoring circuitry 24 contains an RF detector 50 that receives theoutput signals of amplifiers 42 and 44. The RF detector 50 then feedsthe received signal to status monitor circuit 30 and AGC controlcircuitry 52. As a result of the signal being received from RF detector50, AGC control circuit 52 adjusts the attenuation of inserter 36, tovary the gain of amplification circuitry 20.

Status monitor circuit 30 receives on line 61 a DC signal having a firstreference voltage level. The first voltage level is generated by pulldown resistor 58, physically disposed on reverse path circuit 26, andpull up/pull down resistor network 63 disposed on monitoring circuitry24. Status monitor circuit 30 receives through auto amplifier detectline 67 a DC signal having a second voltage level. The second voltagelevel is generated by pull up/pull down indicator circuit 64 that isalso disposed on monitoring circuit 24. If removable AGC controlcircuitry 52 is not installed, status monitor circuit 30 is fed a DCsignal having a third voltage level on AGC mode line 77. The thirdvoltage level is generated by a pull-up resistor 79. If AGC controlcircuit 52 is installed, status monitor circuit 30 is fed on line 77 aDC signal having a voltage level set by pull down resistor 62, which isshunted to ground.

Reverse path circuit 26 includes a coupler 66, which receives thereverse path RF signal from filters 46 and 48 and feeds the RF signalthrough reverse amplifier 68 through reverse filter 49 to headendcontroller 12. Status monitor circuit 30 feeds a status signalcontaining an indication of the signals on lines 67, 77, and 61 as wellas an indication of the detected output-configuration of amplifier 10.This status signal is fed through reverse amplifier 68 and reverse pathfilter 49 to the headend controller 12.

Resistors Rv and Rg represent resistors on the motherboard of amplifier10. Rg is preferably a fixed preset value, and the value of Rv ispreferably set as a function of the number of amplifier outputs (i.e., asingle, a dual, or a triple output). Resistor 62 is disposed withinremovable AGC control circuit 52. AGC control circuit 52 may be added tothe amplifier 10 either during the amplifier production or after theamplifier 10 has been installed in the field.

Referring to FIG. 2, there is shown the status monitoring circuit 30,having a controller 70 that reads the DC signals from the AGC controlcircuit 52 through analog-to-digital (A/D) converter 72 and the DCsignal from the first reference voltage level 64 through A/D converter74. Controller 70 reads the DC signal on line 67 through A/D converter71. Controller 70 is connected to a test interface 76, where thecontroller 70 sends and receives signals to the test interface 76 topermit a technician to connect test equipment thereto that indicates theAGC control circuit 52 and indicator circuit 64 configuration.Controller 70 uses A/D converter 80 to read values from the RF detector50, and to read and store the value of the signal from A/D connector 80and detected RF values into RAM memory 78.

In other alternate embodiments of the invention (not shown), moduleshaving circuits (other than reverse path circuit 26) may be connectedinto the line amplifier 10, and the configuration and function of thesemodules may be detected using an auto module type detect circuit.Referring to FIG. 1, the auto module type detect circuit 75 includes A/Dconverter 74, line 61, and circuit 63. The auto module type detectcircuit 75 monitors the type of module (i.e., distribution reverseamplifier or fiber module) that is installed in amplifier 10 andprovides a signal to controller 70 (FIG. 2) indicating thepresence/absence of such modules. Controller 70 then feeds this signalindicating the presence/absence of such modules to the headendcontroller 12. This indication will aid in determining the appropriateamplifier configuration for proper system configuration at the headendcontroller 12. Additional types of modules may be added in the future.

The following tables 1-3 describe exemplary voltage levels of signalsdetected by the status monitor circuit 30 for the differentconfigurations of the amplifier 10. The status monitor circuit 30 canread the voltage level of these signals and encode the data to informthe headend controller 12 of the amplifier's configuration.

Circuit 75 contains a pull-up/pull-down resistor 63 connected to line 61to amplifier 10. Also, different values for resistor 58, shunted toground, will be connected to status monitoring line 61 in each of themodules to indicate different module types. Table 1 indicates preferredvoltages for the DC signal on line 61 for the corresponding type ofmodule types. An example module type having reverse path circuitry 26 isshown in FIG. 1.

TABLE 1 Module Option Card Types Line 61 Voltage (V) with V_(cc) at +5 VModule Type 1.38-1.64 Fiber Module + Reverse Switch 1.85-2.15 FiberModule 2.33-2.67 Reverse Module + Reverse Switch 3.78-4.24 ReverseModule

Line 67 is used by the status monitoring circuit 30 to enable monitoringof the output configuration type of amplifier 10 (i.e.,_single, dual, ortriple output) that is installed. Voltage level of the DC signal read online 67 will aid the controller 70 in determining the amplifier outputtype for proper amplifier configuration. Additional types of amplifiersmay be added in the future. Pull-up resistor (20 kΩ, 1%) Rv shouldconnected to this amplifier detect line 67. Different resistor values,Rg to ground will also be present on this amplifier detect line 67 inthe mother board to indicate the different amplifier output types. Table2 indicates preferred different voltages on the amplifier detect line 67and the corresponding amplifier output type.

TABLE 2 Amplifier Station Types Line 67 Voltage (V) with power at +5 VAmplifier Type 0.20-0.59 Single 0.89-1.11 Dual 1.38-1.64 Triple

An AGC mode detect line 77 is used by the status monitoring circuit 30to detect the presence or absence of the AGC control circuit 52 and willenable the status monitoring circuit 30 to detect if the amplifier's AGCcontrol circuit 52 is in a thermal mode or an auto mode. A pull-upresistor 79 and a shunt resistor 62 is placed on this AGC mode line 77.Resistor 62 will preferably have a value of approximately 80 Ω when AGCcontrol circuit 52 contains the AGC function, and will preferably have avalue of approximately 20 kΩ when the AGC control circuit 52 contains athermal AGC. Additionally, resistor 62 is preferably an open circuitwhen the AGC function is not present. Table 3 indicates the threepossible states and corresponding voltage levels for the DC signals onthis AGC mode line 77.

TABLE 3 AGC Operation Line Voltage (V) AGC Operation 4.0-5.0 No AGCInstalled 2.0-3.0 Thermal   0-1.0 Auto

While the principles of the invention have been made clear in theillustrated embodiments, there will be immediately obvious to thoseskilled in the art many modifications of the structured arrangements,proportions, elements, materials, and components used in the practice ofthe invention, that are particularly adapted for specific environmentsand operational requirements without departing from those principals.The appended claims are therefore intended to cover and embrace any suchmodifications within the limits of the true spirit and scope of theinvention.

What is claimed is:
 1. A line amplifier for receiving forward andreverse signals and for transmitting amplified forward and amplifiedreverse signals, the line amplifier having an output configuration thatis one of a single output, a dual output, or a triple output fortransmitting portions of the amplified forward signals, the lineamplifier further including a monitoring circuit for detecting theoutput configuration and, the line amplifier comprising: an autoamplifier detect line having an output configuration voltage, whereinthe output configuration voltage is indicative of one of the singleoutput, the dual output, or the triple output; and a controller fordetermining the output configuration based on the output configurationvoltage, wherein subsequent to determining the output configuration ofthe line amplifier, the controller sends a status signal indicating theoutput configuration along with the amplified reverse signals.
 2. Theline amplifier of claim 1, further including an amplification circuithaving an adjustable gain level for amplifying the forward signals, theline amplifier further comprising: an RF detector coupled to the outputof the amplification circuit for receiving a portion of the forwardamplified signals; and a removable AGC control circuit coupled to the RFdetector for adjusting the amplification circuit that subsequentlyadjusts the gain level of the forward signals dependent upon anyvariations in comparison with the received portion of amplified forwardsignals, wherein the controller is coupled to the removable AGC controlcircuit and an AGC voltage source, and wherein the controller receivesan AGC voltage that indicates one of the presence and the absence of theremovable AGC control circuit, and wherein the controller sends an AGCcontrol circuit status signal along with the amplified reverse signals.3. The line amplifier of claim 2, wherein when the removable AGC controlcircuit is present, the controller receives a thermal mode voltage thatindicates whether the removable AGC control circuit is a thermal modeAGC control circuit.
 4. The line amplifier of claim 2, wherein when theremovable AGC control circuit is present, the controller receives anauto mode voltage that indicates whether the removable AGC controlcircuit is an auto mode AGC control circuit.
 5. The line amplifier ofclaim 1, further including a module type that may be one of a fibermodule and reverse switch, a fiber module, a reverse module and areverse switch, and a reverse module, the line amplifier furtherincluding: a first reference voltage level circuit for providing amodule type voltage that is indicative of the included module type tothe controller, wherein the controller sends a module type status signalalong with the amplified reverse signals.
 6. A line amplifier forreceiving forward and reverse signals and for transmitting amplifiedforward and reverse signals, the line amplifier having a configuration,the line amplifier including a monitoring circuit for indicating theconfiguration to a headend controller, the monitoring circuitcomprising: a status monitor circuit for generating voltages thatindicate a specific configuration of the line amplifier; a controllerfor receiving the voltages and for transmitting status signals that area function of the received voltages to the headend controller, wherebythe headend controller determines the configuration of the lineamplifier via the transmitted status signals.
 7. The line amplifier ofclaim 6, wherein the voltages include an AGC control circuit voltage, anoutput configuration voltage, and a module type voltage.
 8. The lineamplifier of claim 7, wherein the AGC control circuit voltage isprovided by a removable AGC control circuit.
 9. The line amplifier ofclaim 8, wherein the AGC control circuit voltage is indicative of athermal mode AGC control circuit.
 10. The line amplifier of claim 7,wherein the AGC control circuit voltage is indicative of an auto modeAGC control circuit.
 11. The line amplifier of claim 6, wherein theoutput configuration voltage is indicative of one of a single outputconfiguration, a dual output configuration, and a triple outputconfiguration.
 12. The line amplifier of claim 6, wherein the moduletype voltage is indicative of one of a fiber module and a reverseswitch, a fiber module, a reverse module and a reverse switch, and areverse module.